Earth’s Interior(What’s down there below us?)

There are 4 main layers inside Earth

How THICK are the layers?(entire Earth is ~ 8000 miles wide)

Crust: oceanic crust 3-6 miles thick continental crust 6-30 miles thick

Mantle: about 1700 miles thick(2/3 of Earth’s mass)

Outer core: about1400 miles thick

Inner core: about1500 miles thick

How HOT are the layers?

Crust: 0oC at surface 400oC where it contacts mantle

Mantle: ~500oC to~3700oC deeper down

Outer core: ~4000oC

Inner core: ~7000oC(hotter than the surface of the sun!!)

What are the layers made of?

Crust: Rock

Mantle: Dense rock

Outer core: Liquid metal (iron) !!

Inner core:Solid metal (mostly iron)

Of course, it’s not quite that simple:

The “lithosphere” is the crust + part of the upper mantle.It is made of rock and is brittle. The “plates” of the earth’s crust make up the lithosphere.

Below the lithosphereis a softer layer calledthe “asthenosphere”.

In the asthenosphere,The rock is near it’s melting point, and flows very slowly, kindof like asphalt or tar.

This graph shows why there is a layer of soft, partially melted rock (the ASTHENOSPHERE) in the top part of the mantle of the earth.

From 100 to 200 km (60-120 miles) below the surface, the temperatures are above the melting point of the rock - even at the very high pressure at this depth.

This layer - the ASTHENOSPHERE - is what the plates of the crust “float on” and explains why they can move around.

MELTINGPOINT OFROCK(yellow)

ACTUALTEMP(green)

Why the partly melted asthenosphere??

Finally – a very cool map showingthickness of earth’s crust (in km)

Continental crustis thick.

Oceanic crustis thinner